Pin greptimedb's version in e2e test

[waynexia]

Maybe we should pin the db version in the e2e test to also prevent future breaking changes. As those CI are not run in the main repo against every new commit.

Context: #195 (comment)

[waynexia]

I found these two options, but I'm not sure which to specific, or both? cc @zyy17

      --greptime-bin-version string                The version of greptime binary(can be override by config file).
      --greptimedb-chart-version string            The greptimedb helm chart version, use latest version if not specified.